1. Field of the Invention
The present invention concerns a fast photopolymerization and/or curing process for making urethane, thiourethane and episulfide polymers and copolymers.
The invention also concerns a process for making an optical article, in particular an ophthalmic lens, through a fast photopolymerization and/or curing process.
2. Description of Related Art
Various polymer materials have been used for making optical lenses such as ophthalmic lenses. These materials include polymers and copolymers of (meth)acrylates, urethanes, thiourethanes, epoxides and episulfides.
Polymerization of the starting monomers and oligomers or crosslinking of the oligomers and polymers have been typically carried out using free radical thermal initiators or free radical and cationic photoinitiators.
Anionic photopolymerization and/or curing of certain monomers in the presence of an anionic photoinitiator is also known.
U.S. Pat. No. 5,652,280 discloses anionic photopolymerization and/or curing of ethylene, 1,3-dienes, styrene, (meth)acrylates and (meth)acrylonitriles, in the presence of an anionic photoinitiator. The photoinitiator is an inorganic transition metal complex that releases a nucleophilic anion when irradiated with visible or ultra-violet radiation. The inorganic complexes used in U.S. Pat. No. 5,652,280 are Cr complexes, Pt complexes and cyclopentadienyl Fe or Ru complexes. These anionic photoinitiators were used for polymerizing ethyl α-cyanoacrylate.
U.S. Pat. No. 5,691,113 discloses a process for polymerizing a monomer or oligomer or crosslinking an oligomer or polymer, in the absence of protic solvents, comprising irradiating a mixture of a monomer, oligomer, or polymer in the presence of an inorganic transition metal complex. The complex is selected from trans-[Cr(NH3)2(NCS)4]−, trans-[Cr(en)2(NCS)2]+, trans-Co(en)2Cl2+, trans-Cr(cyclam)Cl2+, trans-Cr(cyclam)(NSC)2+, trans-Co(cyclam)Cl2+, trans-Cr(R)2(OH)2+, trans-Cr(R)2(OH)H2O2+, trans-Cr(R)2(OH)Cl+, and Pb(OH)62−wherein R is ethylenediamine or 1,3-propylenediamine. The examples describe anionic photopolymerization of ethyl α-cyanoacrylate in the presence of some of the above photo initiators.
U.S. Pat. No. 5,877,230 discloses anionic photopolymerization and/or crosslinking of the same monomers, oligomers and polymers, in particular ethyl α-cyanoacrylate, than the above mentioned patents using cyclopentadienyl metallo complexes as photoinitiators.
U.S. Pat. No. 5,973,098 discloses a thermal fast curing process of polyurethane lenses using a thiocyanate anion to activate the polymerization of the starting monomers. No photopolymerization is mentioned.
The entire contents of each of the above-cited patents are incorporated herein by reference.